Lichen planus is a chronic inflammatory papulosquamous condition that may affect the cutaneous or mucosal surfaces. Systemic viral infections with hepatitis B and hepatitis C have been implicated in disease pathogenesis by modifying self-antigens on the surface of basal keratinocytes. Although the incidence is low, lichenoid reactions have also been reported to occur following immunisations with hepatitis B vaccine and rarely with measles-mumps-rubella, diphtheria-tetanus-pertussis-polio and influenza vaccine.
We present a case of 54 year old female who developed a localised eruption of violaceous pruritic plaques on L) medial arm and axillary wall one month following administration of the inactivated influenza vaccine. The influenza vaccine was indicated for routine prophylaxis in the setting of type II diabetes and administered via the L) deltoid. The patient was otherwise well at the time of symptom onset. Histopathology confirmed the diagnosis of lichen planus. The disease persisted for at least two years and was responsive to potent topical corticosteroids. It is postulated that the inactivated vaccine may represent a trigger necessary for immune alteration. This case highlights that although the influenza vaccine is effective and safe, rarely it may be associated with adverse cutaneous reactions such as lichen planus, which is not widely recognised.